code: def warn_if_fish(executable):
      if (
          executable is None
          or os.path.basename(os.path.realpath(executable)) != "fish"
      ):
          return
  
      logger.warning(
          "DVC detected that you are using fish as your default "
          "shell. Be aware that it might cause problems by overwriting "
          "your current environment variables with values defined "
          "in '.fishrc', which might affect your command. See "
          "https://github.com/iterative/dvc/issues/1307. "
      )
  
file_path: dvc/dvc/stage/run.py
imports: import os
  import signal
  import subprocess
  import threading
  from dvc.log import logger
  from dvc.utils import fix_env
  from .decorators import unlocked_repo
  from .exceptions import StageCmdFailedError
label_desc: Use image node_id 2 for calling a global function with example usage: warn_if_fish(executable) without return types